Cluster-based And Energy-balanced Time Synchronization Algorithm For Wireless Sensor Network

As one of the current research hotspots attracting serious concern, wireless sensor network which integrates sensors, embedded systems, wireless communication and networking, serves as an important role in people’s daily life and industrial production activity. Time synchronization technology is one of the key supporting technologies in wireless sensor network, and it is a necessary condition for the normal operation of the applications of wireless sensor network. However, the characteristics of the limit of energy, volume, communication capabilities of wireless sensor network nodes challenge to the design of time synchronization algorithms. Therefore, it is significant to study the time synchronization algorithm which adapts to the characteristic of time wireless sensor network.For the shortcomings of the existing synchronization algorithms, considering the requirements on the energy consumption and synchronization precision, a cluster-based and energy-balanced synchronization algorithm for wireless sensor networks is proposed in this paper. Based on hierarchy clustering topology, the synchronization process of the entire network includes cluster-inter synchronization phase and cluster-intra synchronization phase. In the cluster-inter phase, it adopts pairwise broadcast mechanism to finish the synchronization between the sink node and cluster heads through dynamically establishing a hierarchical topology. In the cluster-intra phase, it finishes the synchronization between cluster heads and cluster members by the combination of bidirectional pair-wise synchronization and reference broadcast synchronization mechanism. At the same time, a replier is selected according to the residual energy of cluster members to synchronize to cluster head using bidirectional pair-wise mechanism, while others are synchronized to cluster head using reference broadcast mechanism. To reduce synchronization overhead, the synchronization information is piggybacked in the broadcast packet of the next synchronization cycle. Simulation results show that the algorithm can decrease communicaiton overhead, balance nodes’energy consumption and reduce multi-hop error.In addition, in the algorithm based on hierarchical clustering topology, when the cluster head synchronizes to the sink node by multi-hop, the uncertain time delay caused by synchronization packets retransmission has a serious impact on synchronization precision. The cluster-based and energy-balanced synchronization algorithm for wireless sensor network can eliminate send time delay through the pairwise broadcast mechanism, however, the receive time delay still has a great impact on the precision. Therefore, a multi-hop synchronization algorithm is proposed. The algorithm adopts Bayesian estimation to estimate the receive time delay to get a more accurate value of time delay, which can reduce the synchronization error. Simulation results show that the algorithm based on Bayesian estimation can indeed significantly improve synchronization precision.